Walking Beans, Hair, and Reproductive Samples: From Pesticides to Public Health
Professor of Environmental Health Sciences; Senior Associate Dean for Research
As a teenager growing up in rural Iowa, John Meeker spent countless hours in the corn and soybean fields doing farm work to make money. "We would often be out 'walking beans,' where you go row by row through soy fields to kill weeds," he says. He and his friends would receive an unmarked bottle of liquid and would either walk or ride a tractor as they sprayed.
"We were a bunch of adolescent boys, so occasionally we'd spray each other for a laugh," Meeker recalls.
Meeker eventually realized that these seemingly casual chemical exposures were potentially dangerous. In college, Meeker initially majored in engineering, "which was a good fit academically but didn't stir my passion," he says. He wanted a field where he could apply his problem-solving skills to human health issues and began work on a master's program in environmental science and engineering. "That got me looking at what types of things are harmful to humans via exposures at work and how this could impact their health," he says.
He went on to a doctoral program in exposure, epidemiology, and risk, where he began doing the types of research he does now—analyzing the sources, amounts, and consequences of human exposure to environmental and occupational contaminants, with a special interest in chemicals routinely encountered by average consumers such as pesticides, phthalates, heavy metals, and flame retardant chemicals.
It Takes a Village—and Some Hair
Much of Meeker's research looks at how environmental exposures affect reproductive health and child development. For years, he has co-led the large PROTECT study in Puerto Rico, working with a pregnancy cohort to track preterm births. "When we started working there, they had close to a 20% rate of preterm birth. We're at 12% in the US, and even that is really high," Meeker says.
In two decades, the rate in Puerto Rico had spiked—nearly doubling—and it was vital to find out why. Meeker's team collected data on the local environment, looking for potential exposure scenarios in people's daily lives. Meeker uses state-of-the-art biomarkers to help track exposures. "Urine, blood, hair—all kinds of bio-samples can tell us what people have been exposed to and what might be happening in their body," he says. "It's a rapidly developing field and it's exciting right now." They began recruitment for the study nearly a decade ago and are now following children born during the study.
From the outside, a study spanning ten years or more might seem ponderous. To those involved, says Meeker, a team study like this is actually a remarkably dynamic way to do research: "Public health nurses do recruitment and conduct interviews. They do outreach activities with social scientists and form strong bonds with study participants. A host of field researchers do different types of research as required by the project. In Puerto Rico, we have environmental engineers doing water science and remediation work alongside our work. There is a toxicology project, led by fellow EHS faculty member Dr. Rita Loch-Caruso, which helps inform the biological mechanisms that may explain the associations we observe in the human study. Then there are the data scientists working to combine and make sense of the diverse array of information being collected."
Meeker says team science is not only effective but can be rewarding well beyond the research. "We've built an amazing collaboration with multiple organizations and institutions of higher learning in this study. And in the ongoing aftermath of Hurricanes Irma and Maria, it has been this same team going outside of the research and coming together to help our participants, study staff, and their communities," he says.
Subtle Science with Powerful Effects
The Puerto Rico study is far from over, but they have published some interesting findings along the way, such as levels of exposure to certain chemicals and data pointing to likely sources of those exposures. And the rate of preterm births has decreased to 12–15% each year, which is a promising sign to all involved but by no means the end, since that rate is still far too high.
Meeker leads eight active research studies spanning a range of exposures and life stages. Each project has its own complexity and its own ability to open up new scientific insights. A Boston-based project with people going through assisted reproduction gave Meeker and colleagues access to biomarkers that normally are difficult to procure— such as blood and semen samples from males, egg retrieval information from females, and measures of embryo development. "It's a huge amount of data, and it lets us look at exposure in a way that improves our understanding of how human reproduction works in various environments," says Meeker.
Because this data is broken up into life stages—gametes, fertilized eggs, blastocysts, embryos—Meeker and his collaborators can observe levels of detail not available when tracking other types of pregnancies. "With IVF data, if a certain endpoint looks particularly sensitive, it tells us a lot. A chemical toxicant could be impacting only the male or female side of conception, and we'd know which part of the process to study. And we could see post-conception at very specific developmental stages impacting growth and health," explains Meeker.
Epidemiology and exposure science can be very subtle, Meeker admits: "With so many moving pieces, you're often looking at a very small section of an overall picture. You might be doing a study that doesn't immediately solve a major problem, but many times the goal is to add to the evidence on a topic that will eventually affect how policy and other decisions are made."
The Adventurous Side of Exposure Science
On the flip side, solutions can be remarkably simple and have immediate impact. "In one construction setting, we began recording data and saw exposure levels through the roof with workers doing a job a certain way," Meeker reports. "We introduced a shop-vac-style ventilation system to the same job and were able to show a 95% reduction in exposure. Soon after we saw people at other sites using that information and reducing harmful exposure."
Data collection also provides a bit of adventure. "Construction health work has taken me all over to do some crazy stuff," says Meeker. "I've had to hook up sampling pumps to workers getting ready to sand-blast paint off a bridge on a major New Jersey highway, grind mortar between bricks on historical building renovations in Boston, Philadelphia and Chicago, or weld steel in power plants or on a new building, even including here at SPH when the tower was being built."
But going out on site and hooking up sampling units is not only interesting science—it also provides perspective: "You get a remarkable appreciation for the duration and intensity of the work being done in construction, as well as the high level of skill many of these workers bring to their job every day."
When Meeker is able to improve the safety of those workers, he knows his own job was well done. Some of the worker protections he develops may well help the kids out walking beans in Iowa today, as could the longer-term exposure and epidemiology studies he and his colleagues are conducting.
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